Method for transportation of viscous hydrocarbons by pipeline

ABSTRACT

A method of transporting viscous hydrocarbons which involves introducing into a pipeline or well-bore with the viscous hydrocarbons a solution containing an oxyalkylated anionic surfactant such as sodium nonyl phenol polyoxyethylene sulfonate or a mixture of such surfactants and, optionally, with an alkalinity agent thereby forming a low-viscosity, salt-tolerant oil-in-water emulsion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved method for transportinghydrocarbons through a pipeline or a well-bore. More particularly, thisinvention relates to the introduction into a pipeline of a viscoushydrocarbon or mixture of hydrocarbons together with an aqueous solutionof an oxyalkylated anionic surfactant or a mixture of oxyalkylatedanionic surfactant, whereby a low-viscosity, salt-tolerant oil-in-wateremulsion is formed which facilitates movement of the hydrocarbon in thepipeline. Optionally, the solution may contain an alkalinity agent suchas an alkali metal hydroxide.

2. Description of the Prior Art

The transportation of heavy crudes by pipeline is difficult because oftheir low mobility and high viscosity. The ususal methods to facilitatethe flow of heavy crudes have included cutting them with lighterfractions of hydrocarbons. However, the procedures involve the use ofrelatively large amounts of expensive hydrocarbon solvents to transporta relatively cheap product. This practice also necessarily requires theavailability of the cutting hydrocarbon solvents which, in someinstances is inconvenient.

Another method to assist the flow of hydrocarbons in pipeline is theinstallation of heating equipment at frequent intervals along thepipeline, whereby the crude is heated to reduce is viscosity and therebyfacilitate its transport.

Heaters employed for this purpose can be operated by withdrawing some ofthe crude being transported for use as fuel. However, this procedure mayresult in the loss of as much as 15 to 20% of the crude beingtransported.

Other methods to facilitate transport of heavy crudes have employedthermal viscosity breaking which, however, produces substantial amountsof gas.

It is known that substantial amounts of water may be introduced into apipeline containing a stream of viscous crude flowing therethrough toreduce the drag on the stream and thus facilitate the flow through thepipeline. This has been done by the addition of water together withcrude into the pipeline such that a water-in-oil emulsion is formed.

It is thus an object of the present invention to provide a transportmethod for viscous crudes which are not easily emulsifiable especiallyin the presence of water with substantial salt content whereby they canbe more easily transported by piepline at a high thru-put rate.

SUMMARY OF THE INVENTION

This invention relates to a method for transporting viscous hydrocarbonssuch as crude oil in which the hydrocarbons together with an aqueoussolution of an oxyalkylated anionic surfactant or a mixture ofoxyalkylated anionic surfactants is introduced into a pipeline therebyforming a low-viscosity, salt-tolerant oil-in-water emulsion.Optionally, the aqueous solution may contain an alkalinity agent.

DESCRIPTION OF THE INVENTION

As previously pointed out, this invention is concerned with a method oftransportation via pipeline of viscous oils in an oil-in-water emulsionwherein the water phase is formed using highly saline and/or hard water,e.g., water containing appreciable quantities of sodium chloride and/orwater-soluble salts of divalent cations such as calcium or magnesium.

One group of anionic oxyalkylated surfactants which are especiallyuseful in the process of this invention include sulfonate compounds ofthe formula:

    RO(CH.sub.2 CH.sub.2 O).sub.x CH.sub.2 CH.sub.2 SO.sub.3 M,

where R is selected from the group consisting of alkyl of from 10 to 25carbon atoms; ##STR1## where R_(a) is an alkyl of from 8 to 25 carbonatoms and ##STR2## where R_(b) is an alkyl of from 8 to 25 carbon atoms,x is an integer of from 1 to 15 and M is a metallic cation such assodium, potassium, lithium or the ammonium ion.

Another group of anionic oxyalkylated surfactants which are suitable foruse in the process of this invention include block-type sulfonatecompounds of the formula:

    R.sub.c O(C.sub.2 H.sub.4 O).sub.r --(C.sub.3 H.sub.6 O).sub.s --(C.sub.2 H.sub.4 O).sub.t CH.sub.2 CH.sub.2 SO.sub.3 M,

wherein R_(c) is selected from the group consisting of alkyl of from 10to 25 carbon atoms, ##STR3## wherein R_(d) is alkyl of from 8 to 25carbon atoms and ##STR4## wherein R_(e) is alkyl of from 8 to 25 carbonatoms; r is an integer of from 2 to about 10, s is an integer of from 1to about 8, t is an integer of from 2 to about 10 and the sum of r + s +t is not more than 20, wherein at least 60 percent of the oxyalkyleneunits are oxyethylene units and M is a metallic cation selected from thegroup consisting of sodium, potassium, lithium or an ammonium ion.

Block-type sulfonate surfactants as described above may be prepared byfirst condensing ethylene oxide with a suitable initiator in thepresence of, for example, about 0.12 weight percent of sodium hydroxidein a stirred autoclave maintained at 95°-100° C. After devolatilizingthe resulting product to remove low boiling product, if desired, asecond condensation reaction is conducted with propylene oxide under thesame conditions and finally a third condensation is conducted withethylene oxide. After the block-type oxyalkylated precursor has beenprepared, it is reacted with sulfurous oxychloride (i.e., SOCl₂) toreplace the terminal hydroxyl group with chlorine and this intermediatemay then be reacted with sodium sulfite to form the desired sulfonate.This sulfonation reaction is below where, for purposes of illustration,the sulfonation of polyethoxylated alkylphenol is set forth: ##STR5##These same sulfonates can also be prepared by first forming thecorresponding sulfate salt and then reacting the sulfate salt withsodium sulfite. This last-mentioned reaction is considered lessdesirable than the SOCl₂ -Na₂ SO₃ method since drastic reactionconditions must be employed to force the sulfate reaction to completion.

Another suitable group of anionic oxyalkylated surfactants for use inthis invention include sulfate compounds of the formula:

    R.sub.f O(CH.sub.2 CH.sub.2 O).sub.m SO.sub.3 M

wherein R_(f) is selected from the group consisting of alkyl of from 10to 25 carbon atoms and ##STR6## wherein R_(g) is alkyl of from 8 to 25carbon atoms, m is an integer of from 1 to about 14 and M is a metalliccation such as sodium, potassium, lithium or the ammonium ion. Forexample, sodium tridecyl-polyoxyethylene sulfate and potassiumnonylphenol polyoxyethylene sulfate are preferred sulfate-typesurfactants.

In this invention the aqueous solution added to the viscous hydrocarbonwill generally range from a minimum of about 8 percent by volume basedon the volume of the hydrocarbon introduced into the pipeline up to amaximum of about 60 percent or more by volume with the preferred amountbeing about 20 to about 40 percent by volume on the same basis. In theaqueous solution the concentration of the anionic oxyalkylatedsurfactant or mixtures thereof will range from about 0.01 to about 2.5weight percent.

If employed, the alkalinity agent which can be selected from the groupconsisting of sodium hydroxide, potassium hydroxide and lithiumhydroxide will range in concentration from about 0.01 to about 1.0weight percent.

The following example illustrates an embodiment of this invention whichis to be considered not limitative:

EXAMPLE

An aqueous solution comprising about 0.5 weight percent of an anionicsurfactant having the formula: ##STR7## 0.12 weight percent of a sulfatesurfactant having the formula

    C.sub.12 H.sub.25 O(CH.sub.2 CH.sub.2 O).sub.4 SO.sub.3 K,

is formed by mixing together at a temperature of about 25° C. theabove-named ingredients with brine having a salinity and hardness ofabout 1.65 weight percent. The thus-formed aqueous solution isintroduced into a pipeline together with heavy Utah crude to give anoil-in-water emulsion in which the volume percent of the aqueoussolution based on the volume of the crude is about 26 percent. Anappreciable saving in horsepower requirement for pumping 4,000barrels/day of the emulsion through the pipeline over the requirementfor the same amount of this Utah heavy crude under the same condition isachieved.

What is claimed is:
 1. In the transportation of viscous hydrocarbons bypipeline, the improvement which comprises forming an oil-in-wateremulsion by inroducing into the pipeline with said hydrocarbons anaqueous solution of an oxyalkylated anionic surfactant wherein theamount of the aqueous solution of the surfactant introduced into thepipeline with the said hydrocarbon ranges from about 8 to about 60percent by volume based on the volume of the hydrocarbon introduced intothe pipeline, wherein the concentration of the said surfactant in theaqueous solution is from about 0.01 to about 2.5 weight percent andwherein the oxyalkylated surfactant is a compound of the formula:

    R.sub.c O(C.sub.2 H.sub.4 O).sub.r --(C.sub.3 H.sub.6 O).sub.s --(C.sub.2 H.sub.4 O).sub.t CH.sub.2 CH.sub.2 SO.sub.3 M,

wherein R_(c) is selected from the group consisting of alkyl of from 10to 25 carbon atoms; ##STR8## wherein R_(d) is alkyl of from 8 to 25carbon atoms, and ##STR9## wherein R_(e) is alkyl of from 8 to 25 carbonatoms; r is an integer of from 2 to about 10; s is an integer of from 1to about 8; t is an integer of from 2 to about 10, and the sum of r +s + t is not more than 20, wherein at least 60 percent of theoxyalkylene units are oxyethylene units and wherein M is selected fromthe group consisting of sodium, potassium, lithium and the ammonium ion.2. In the transportation of viscous hydrocarbons by pipeline, theimprovement which comprises forming an oil-in-water emulsion byintroducing into said pipeline with said hydrocarbon an aqueous solutionof from about 0.01 to about 2.5 weight percent of an oxyalkylatedanionic surfactant and about 0.01 to about 1.0 weight percent of analkalinity agent selected from the group consisting of sodium hydroxide,potassium hydroxide and lithium hydroxide, wherein the amount of theaqueous solution of the surfactant introduced into the pipeline with thesaid hydrocarbon ranges from about 8 to about 60 percent by volume basedon the volume of the hydrocarbon introduced into the pipeline, whereinthe oxyalkylated surfactant is a compound of the formula:

    R.sub.c O(C.sub.2 H.sub.4 O).sub.r --(C.sub.3 H.sub.6 O).sub.s --(C.sub.2 H.sub.4 O).sub.t CH.sub.2 CH.sub.2 SO.sub.3 M,

wherein R_(c) is selected from the group consisting of alkyl of from 10to 25 carbon atoms; ##STR10## wherein R_(d) is alkyl of from 8 to 25carbon atoms and ##STR11## wherein R_(e) is alkyl of from 8 to 25 carbonatoms; r is an integer of from 2 to about 10, s is an integer of from 1to about 8, t is an integer of from 2 to about 10, the sum of r + s + tis not more than 20, wherein at least 60 percent of the oxyalkyleneunits are oxyethylene and wherein M is selected from the groupconsisting of sodium, potassium, lithium and the ammonium ion.